The present invention relates to an improvement of a pressure control valve to be provided in a ventilation path between a fuel tank and a canister for controlling an internal pressure of the fuel tank.
Japanese Patent Publication (Tokkai) No. 09-60744 discloses a pressure control valve (also called as a check valve, etc.) to be provided inside a ventilation path between a fuel tank and a canister for controlling an internal pressure of the fuel tank.
Such a conventional valve includes the first body, the second body, a positive pressure valve body, the first spring for urging the positive pressure valve, a negative pressure valve body, and the second spring for urging the negative pressure valve. That is, the conventional valve has relatively many parts, thereby requiring extra labor for assembly and making it difficult to reduce a cost.
In view of the problems of the conventional valve, an objective of the present invention is to provide a pressure control valve for a fuel tank with a minimal number of parts. The control valve opens properly a ventilation path between the canister and fuel tank when an inner pressure of the fuel tank reaches a high pressure level or a low pressure level.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to achieve the above-mentioned objectives, in the present invention, a pressure control valve for a fuel tank includes a valve chamber providing the first communicating portion communicating with a ventilation path to a canister and the second communicating portion communicating with the fuel tank; a hollow first valve member disposed in the valve chamber to be movable up and down; and a second valve member disposed inside the first valve member to be movable up and down. At a bottom of the first valve member, there are provided a valve member for blocking the second communicating portion from inside the valve chamber, the first communicating hole passing through the valve member, and the second communicating hole formed at a position different from the first communicating hole for connecting between inside the first valve member and the valve chamber. Further, the second valve member is arranged to block the second communicating hole from the inside the first valve member, and the first valve member rises to open the second communicating portion when an inner pressure of the fuel tank reaches a certain high level, and also the second valve member rises to open the second communicating hole when the inner pressure of the fuel tank reaches a certain low level.
According to this configuration, when the pressure inside the fuel tank is within a predetermined range, in other words, the fuel tank is not in a certain high or low pressure state, the first valve member closes the second communicating portion from the inside of the valve chamber by its own weight, and at the same time, the second valve member closes the second communicating hole from the inside of the first valve member by its own weight, so that the canister does not communicate with the fuel tank.
When the inner pressure of the fuel tank reaches the predetermined high level, an upward pressure toward the first valve member is applied to a bottom of the first valve member through the second communicating portion, thereby rising the first valve member to open the second communicating portion, so that the canister communicates with the fuel tank.
Further, when the inner pressure of the fuel tank reaches the predetermined low level, the upward pressure toward the second valve member is applied to the second valve through the second communicating hole, thereby rising the second valve member to open the second communicating hole, so that the canister communicates with the fuel tank through the inside of the first valve member and the first communication hole while the first valve member is still at a low position.
That is, it is possible to construct the valve having the above-mentioned pressure controlling function only with the first valve member including the second valve member inside the valve chamber. Thus, the valve can be formed of a minimal number of the parts.
Also, in the pressure control valve for the fuel tank of the present invention, at least one of the first valve member and the second valve member can open the valve through a vibration of the running vehicle. With this configuration, even when the pressure inside the fuel tank is within the range of the pressure where the first valve member and second valve member are not raised, the canister communicates with the fuel tank as needed.
In addition, the pressure control valve for the fuel tank of the present invention includes a lower chamber disposed inside the fuel tank with a bottom of the valve chamber as a top wall of the lower chamber. The valve chamber communicates with the lower chamber through the second communicating portion. Further, a float member is disposed in the lower chamber and constitutes a cut valve for blocking the second communicating portion from the lower chamber side when the fuel flows into the lower chamber to raise the float member.
With this configuration, the cut valve with the function for controlling the inside pressure of the fuel tank through the first valve member and the second valve member can be constituted with a minimal number of the parts.